﻿using System;
using System.Linq;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.Reflection;

namespace Skynet.CommonLibrary
{
   public static class SingleProcess
    {
        /// <summary> 
        /// 该函数设置由不同线程产生的窗口的显示状态。 
        /// </summary> 
        /// <param name="hWnd">窗口句柄</param> 
        /// <param name="cmdShow">指定窗口如何显示。查看允许值列表，请查阅ShowWlndow函数的说明部分。</param> 
        /// <returns>如果函数原来可见，返回值为非零；如果函数原来被隐藏，返回值为零。</returns> 
        [DllImport("User32.dll")]
        private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
        /// <summary> 
        /// 该函数将创建指定窗口的线程设置到前台，并且激活该窗口。键盘输入转向该窗口，并为用户改各种可视的记号。系统给创建前台窗口的线程分配的权限稍高于其他线程。 
        /// </summary> 
        /// <param name="hWnd">将被激活并被调入前台的窗口句柄。</param> 
        /// <returns>如果窗口设入了前台，返回值为非零；如果窗口未被设入前台，返回值为零。</returns> 
        [DllImport("User32.dll")]
        private static extern bool SetForegroundWindow(IntPtr hWnd);
        private const int WS_SHOWNORMAL = 1;

        private static Process RunningInstance()
        {
            Process current = Process.GetCurrentProcess();
            Process[] processes = Process.GetProcessesByName(current.ProcessName);
            return processes.Where(process => process.Id != current.Id).FirstOrDefault(process => Assembly.GetEntryAssembly().Location.Replace("/", "\\") == current.MainModule.FileName);
        }

        /// <summary> 
        /// 显示已运行的程序。 
        /// </summary> 
        private static void HandleRunningInstance(Process instance)
        {
            ShowWindowAsync(instance.MainWindowHandle, WS_SHOWNORMAL); //显示，可以注释掉 
            SetForegroundWindow(instance.MainWindowHandle);            //放到前端 
        }

        public static bool IsSingleProcess
        {
            get
            {
                Process instance = RunningInstance();
                if (instance == null)
                {
                    return true;
                }
                HandleRunningInstance(instance);
                return false;
            }
        }

    }
}
